It's shows the human race mourning the "DEATH" of the Master Chief and looking like they have lost the battle already.
Could this be the end as we know it.....???. The video does show the Master Chief running for his life before the area around him gets glassed and then crushed from falling debris.
Could this mean that the next two games after, could be without the Master Chief?. Only way to find out is by buying the game on the 27th October.